This invention pertains generally to the cooling of a hermetic compressor pump used in cryogenic refrigeration. Typically, this pump compresses a mixture of oil and helium. The purpose of the oil is to absorb the heat produced in compressing helium and to provide lubrication to the pump. From the compressor, the mixture exits a feed line in which the oil is separated from the mixture. Conventional methods use an oil separator and then an oil adsorber to filter the oil out of the mixture. Once separated, the gas is then pumped to the cold head of a cryogenic refrigerator such as a Gifford-MacMahon cryogenic refrigerator disclosed in U.S. Pat. No. 3,218,815 to Chellis et al. After traveling through the refrigerator, the gas is returned through a return line to start the process over again.
As a result of compressing helium, rather than freon which is used in other refrigeration systems, more heat is produced by the compressor pump. In order to maintain operating efficiency, this heat by-product must be removed.
Presently, there are three traditional methods for removing the heat created by compressing helium. In one, a water jacket is attached to the housing of the pump. This is generally the most common type of conduction cooling. This method, however, requires a seperate water supply and a seperate pump. In another method, convection fins are placed on the pump's housing. A fan is then placed above or below the pump for air cooling. Such arrangements, however, require an appreciable amount of space. In a third method, a desuper-heat pump cools the compressed gas leaving the pump and re-enters the pump to cool the motor windings before leaving the pump to do work. In this method the working gas is heated. Therefore, there exists a need to develop a cooling system which will cool the pump efficiently while achieving a smaller packaging size.